α‑Allyl-α-aryl α‑Amino Esters in the Asymmetric Synthesis of Acyclic and Cyclic Amino Acid Derivatives by Alkene Metathesis

Allylating agents were explored for
the asymmetric synthesis of
α-allyl-α-aryl α-amino acids by tandem N-alkylation/π-allylation. Cross-metathesis of the tandem product
was developed to provide allylic diversity not afforded in the parent
reaction; the synthesis of homotyrosine and homoglutamate analogues
was completed. Cyclic α-amino acid derivatives could be accessed
by ring-closing metathesis presenting a viable strategy to higher
ring homologue of enantioenriched α-substituted proline. The
eight-membered proline analogue was successfully converted to the
pyrrolizidine natural product backbone.